Drying system



' 'il 12 1927. M. MUELLER" DRYING SYSTEM FiledNov. 4. .1926s'sheets-sheetl 1 Apnl 12 1927- L. MUIELLER DRYING SYSTEM Filed Nov 4.192,5

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1 Qua W4 5 v 3w in: W W 7 ill; ||l\| S Q m\ W m 4 r v MW gr W x I V XQXM w R m N u L m 1 mm Q mw Mim Qifl MA Wu l x X e M D m 1 .7 avg 0 an......E "in u w o v o H4 M o o oo R v A a. Q 5 H w m w w QhY PM, o k 1 r sr f v r x 11 Q: p? 1 g q Patented Apr. 12 1927.

uNiTEo Y STATES PATENT OFFICE.

IO BTTZ 1' MU ELLEB, OI SEATTLE, WASHINGTON, ASSIGNOR TO NORTHWESTBLOWER KILN OF PORTLAND, OREGON, A CORPORATION OF WASHINGTON.

name SYSTEM.

"hrplication med November 4, 1926. Serial No. 146,135.

This invention relates to drying systems and it has for its object to socorrelate a plurality of drying agenciesthat their complementaloperation will present marked ad- 6 vantages and economiespver whatwpuld be secured by their operation, smgly.

In a great manytypes of driers, both for. lumber and other materials, aseries or battery of driers are located in adjacent POSI- ltl difl'erentatmospheric conditions in various driers at the same time. As forinstance, the product being dried will be just starting in one chamberor several,- more progressed in others and nearly finished in stillothers of the same battery.

Inasmuch as in all driers wherein the drying process is accomplished atatmospheric pressure, there are waste vapors escaping at certain stagesof the drymg, a considerable amount of hot moist air is being I thrownoff. from some chambers of a bat tery of driersat practically all times.These vapors result from the water in'the' product being evaporated andthe -necessity of removing-such vapor to prevent. the development; of.internal pressure inside the chamber or the a'tm'osphe're becomingsaturatedas the Y liquid water in the products: is: turned into agaseous vapor-by evaporation.

inclu in'g lumber, tl1ere are several stages to the drying process",these stages being'necessary .tofdr'y the --lproduct without -1n ury.

. These stages or periods any one chamber are usually of the followingnature when considered in relation to the balance of the ad- .joiningdriers. v H

(a) The starting stage, when 'the cold product to be dried is warmed upto the center of its bulk at which time a large volume of heatisrequired to heat up the product and also a large volume of atmosphericmoisture is required to prevent surface drying taking place before theproduct is heated throughout its bulk. At-this stage, the drier [can useto advantage the hot moist' exhaust- "apors thrown off by adjoiningdriers as 5 these exhaust vapors will permit the prodvery rapidly with aminimum consumption of a plied heat of any kind (such, for ex-" 'tionsand the product being dried is under.

udri'ers to pour In. raetically .every product thatis dried,

products in other chambers.

net of the drie'rsin question to be heated up pipes) and will alsosupply the necessary moisture to the air with the minimum use of livesteam or other usual humidifying moisture.

(b) The intermediate drying stage, where it is necessary to have ahigher humidity in one driertha'n in other driers in order to protectthe product being dried from injury.

The usual way of producing such' higher humidity condition is by the useof live steam sprayed into the atmosphere, or some similar humidifyingdevice. This can better be'acccmplished by .allowing the exhaust vaporsfrom adjoinin driers to pour into the drier in question because a morepenetrating moisture will be secured and the use of live steam will beavoided or reduced.

(0) The final conditioning stage, where many products when dry require asoftening treatment td relieve the drying strains produced by theremoval of water from their structure. At this stage, the productrequires its surrounding atmosphere to be very moist for a period oftime. This condition is usually produced by flooding the drier with livesteam but could better be accomplished by permitting the nearlysaturated exhaust vapors from the adjoining into the drier in question.Where products of a. different nature are being dried ina battery ofdriers, the products in some chambers will require lower temperaturesand higher humidities than sible. because of this condition to use whatwill constitute exhaust vapor fronri certain' driers for the drying ofthe roduct in-other chambers and even of taking the exhaust vapors jfrom a drier using exhaust vapor from other driers and use it again forstill others requiring lower temperatures and higher humidities thanthis second class.

This low temperature drying being now accomplis hed by live steam ofhigh value, I

could be accomplished at a considerable saving by using the. exhaustvapors now being wasted to the atmosphere.

Further, where a'series of driers are drying products requiringdiflerent atmospheric temperatures and humidities and each ex.- haustingvapors of consequently varying temperatures and humidities the aggregateaccumulated exhaust vapors of all the driers vapors, thereby removingthe necessity as a whole or in part of supplying heat from -othersources such as live steam, for example.

Further, inasmuch as it is necessary in the drying of all products atatmospheric pressure to exhaust definite amounts of evaporated water atcertain stages to make drying possible, it is advisable to prepare meansfor withdrawing such vapors from the prod ucts being dried, toaccelerate their drying. I have chosen to illustrate the inventionapplied to a battery of kilns in which lumber is dried. However, it willbe clear as this description proceeds that the basic principles involvedare applicable to driers, kilns, ovens and the like adapted to handleall sorts of material.

In the drawings- Fig. 1 is a diagrammatic plan view of a battery ofkilns having the invention applied thereto.

Fig. 2 is a partial side elevation thereof. Fig. 3 is a diagrammatic endelevation. Fig. 4 is a longitudinal sectional view illustrating theinvention applied to an external fan-type drier.

Fig. 5 is a diagrammatic cross sectional view of the drier of. Fig. 4. I

Fig. 6 is a view similar to Fig. 5 but illustrating a natural draftdrier.

- tween a plurality of kilns,

Fig. 7 is a view similar to Fig. 6 but illustrating an internal fandrier, and

Fig. 8 is a partial longitudinal section through the drier of Fig. 7.

Like numerals designate corresponding parts in all of the figures of thedrawing.

In the diagrammatic view, Fig. 1, the dotted lines 5 represent thedivision walls be ovens or other drying chambers. I have chosen toillustrate the invention in conjunction with kilns of the generalcharacter of those shown in Patent #1,437,385, issued to me on November28, 1922. Fig. 3 of that patent illustrates the pressure conduit asbeing centrally disposed and the suction conduits as being disposed atthe sides of the kiln, the heated air being discharged upwardly into anopening left in a stack of flat iled lumber, passing outwardly through te pile of lumber and then downwardly along the sides of the pile oflumber to the suction conduits. Fig. 4 of the patent referred todiscloses the reverse of this in that the suction is in the center andthe pressure conduits are at the sides, this arrangement beingparticularly useful in connection with edge piled lumber. Thediagrammatic sectional views 5, 6 and 7 make it clear that the presentinvention is applicable to both types of kilns referred to and inaddition is applicable to many types of driers and ovensother than thoseintended for the conditioning of lumber.

From the foregoing it will be understood that each kiln is provided withmeans for setting up a circulation of air therein, under either naturalor forced draft and these means may be varied within wide-ranges withoutaffecting the applicability of the present invention, which is inaddition to or supplementary to, said circulatory systems. A suctionconduit 6 extends across and is common to all of the battery of kilns 5.Suetion laterals 7 extend longitudinally along the tops of the kilnsfrom the suction conduit and have communication with the tops of thekilns, at intervals, through ports 8. This suction conduit is connectedat one end with the casing 10 of,a fan, driven by a motor or othersuitable means indicated at 11. The pressure side of the fan casing isconnected to a pressure conduit- 12, which extends across and is commonto all of the battery of kilns. Cross connection duct 13 is preferablyemployed and connects pressure duct 12' with the suction duct 6. Thiscross connection is provided with a damper 14 which permits or preventsa circulation of the air through the suction and ressure ducts accordingto the degree to which said damper is opened. Permitting the air torecirculate decreases the suction effect of the fan effective into thevarious driers and preventing recirculation increases said suctioneffect. Conditioning means 15 may be disposed at any suitable point ineither the suction or pressure duct. The conditioning equipment mayconsist of means for cooling, humidifying or dehumidifying the airpassed therethrough. The pressure duct is provided with an exhaust vent17, having a damper 18' therein, which is arranged to open when apredetermined pressure has been built up in the pressure.

conduit to permit the escape of vapor beyond that point. No specificillustration showin the damper employed, has, been given,.smce automaticpressure relief valves are common to-many o thearts. The pressure duct12, which extends across all of the kilns, communicates with the mainsuction conduits 19 of the several kilns through ports 19, which arecontrolled by hapd or automatic-dampers' 20. .The points of commuthe artand are available upon the. public market. It is a matter of choicetoselect the the. circulated vapors.

proper dampers for use in these locations.

lVliile I have stated that a fan is employed, it may be possible to omitthis fan where differences in pressure in the two conduits exist withsufiicient force to'make the use of the fan unnecessary.

In the form of the invention illustrated in Figs. 4 and 5, the maincirculatory system of the individual kiln there shown comprises anexternally located fan 25 which draws vapor through the main suctioncon'- duit 19, past a suitable heating unit (in this case a bank ofsteam pipes 26) and discharges the vapors. from the pressure side of thefan "er'tically into the body of the kiln as indicated by the arrows((1). Thus it will be seen that any air (vapors, etc.) delivered intothe main suction conduit 19 from auxiliary pressure conduit 12 willpartake of any treatment, such as heatin by the coils 26, that is givento -the main liody of vapor travelling in the conduit 19. Thus when thevapor is delivered into the drying chamber of the kiln it will beuniform throughout as to humidity, temperature, etc.

In the form of the invention illustrated in Fig. 6, steam coils 27 aredisposed horizontally and extend longitudinally of the kiln. In Figs. 7and 8, the main circulating fan 20 is internally located with respect tothe kiln and draws the vapors downwardly from the drying chamber of thekiln and forces them upwardly into the drying chamber of the kiln asindicated by the arrows, steam pipes 29 being disposed horizontally andlongitudinally in the path of In this latter form of the invention thepressure conduit 12 of my economizer system is in communication withlongitudinally extending pressure ducts 30 having ports 31 at intervalswhich communicate with the main circulatory sys .tem of the kiln todeliver. auxiliary vapor to the main body of vapor. being circnlatedinthe kiln.

The operation is as follows:

"The fan 10 would be operated at a con stant .or variable speed with thepressure relief exhaust damper 18 set to maintain a constant ressure inthe pressure conduit, also the amper 14 in the cross connection set tomaintam a constant negative pressure in the suction conduit.

This would produce a drawing effect'on all the laterals of the suctionconduit and thence into all driers, where the suction conduit damper21was open; resulting in exhaust vapors from such driers being drawn tothe fan. An acceleration in the drying rate of the product in suchdriers would be thus efiected by the more rapid removal of the moisturethey were losing.

The accumulation of hot moist vapors in the suction conduit, being anaverage of exhaust vapors from all the driers, would be vapors.

This accumulated exhaust vapor of high temperature and humidity(ordinarily If insutficieutly hot,

wasted) would now be available as primary or auxiliary heating, andhumidifying means for use in certain driers operating at stages belowaverage and consequently requiring heat and humidity. The dampers to thepressure conduit on such driers would be opened suflicie'ntly to allowthe most advantageous use of this heat and vapor in the drying of theirproducts. Such driers as are filled with a cold prod uct, whose heating,moistening and drying was to be started, would have the damper from thepressure conduitopened wide allowing the hot, humid vapor to pour intothem in large volumes. The corresponding suction conduit dampers wouldbe open pcrmitting the cold air in the drier to be rapidly withdrawn. Asa result a quick heat and a high humidity would be produced eitherentirely by the use ofthese exhaust vapor; or in combination with livesteam in heating radiation, the result being to decrease 1natcrially theamount of steam required to heat the material and condition it fordrying.

Such driers ot' the battery whose enclosed product was being dried undera condition where additional heat was required to raise the temperatureor where an, even heat beduced, making necessary a final condition ingtreatment, would have all live steam turned off and the pressure conduitdampers opened. The very moist air pouring into the drier would give asuperior conditioning treatment to that usually accomplished byfloodinglthe drier with live. steam and in addition, save such livesteam.

The driers containing material requiring vexce tionally low temperaturesand high humldities would have the pressure conduit dampers openedpermitting the exhaust The exhaust damper in the pressure'conduit beingadjustable would prevent the continuous reclrculation of exhaust vaporsand hence prevent these vapors reaching saturation and make such vaporsalways capable of further drying for this reason. Obviously this usewould make a material saving of live steam now used to dry suchproducts.

Under existing practice with most types of driers, from 2 pounds to 7pounds of live steam are used to evaporate 1 pound of water from aproduct being dried. Of this 2 to '7 pounds of steam, a percentagevarying from 25% to is permitted to escape to the atmosphere in anefi'ort to dry the product rapidly. The saving of as large as possiblean amount of this 'now wasted steam and heat is of course verydesirablel While the suction and pressure conduits, which are common. toa plurality of kilns, have as their prime function the delivery of-waste vapors from one kiln to another kiln,

as described, it is a fact thatan important auxiliary advantage andeffect arises from the fact that the increased circulation set up, actsto markedly accelerate the action of the drier or kiln, with a.corresponding in" crease in efliciency.

The dampers 20 and 21 may serve to render the pressure and suctionconduits 6 and 12' inoperative with respect to any particular kiln.Further I contemplate discharging vapors'directly from any given kiln,into the atmosphere. It is common to provide means for discharging kilnvapors from any given kiln, into the atmosphere, at will. As

one means for accomplishing that result I have indicated vents 8 in Fig.7, which may be closed by closures 8". However, with vents 8 of anygiven kiln, open, and the damper 21 of the said kiln closed, the wastevapors discharged into the kiln would not be recirculated through theauxiliary suction duct 6 but would be discharged through vents 8. Insuchcase the hot, moist, waste vapors entering the kiln from theauxiliary pressure conduit 12 and main pressure con-.

duit 19, would speedily warm up the lumber or other product being driedand force out the cold air from said product. dislodged cold air and thewaste vapors delivered into the kiln, (by this time largely deprived oftheir heat) would pass out ofvents 8* into the atmosphere, it followsthat the lowering of the average temperature in conduit 6 would beavoided. The waste vapors which accomplish the foregoing useful result,might well be those which would otherwise be discharged through exhaustvent 17 and wholly wasted. I am awareof the fact that the patent toDuryea 887,317,

Since this.

discloses a plurality of kilnshaving common suction and pressure ducts.However, the inventive thought in the Duryea patent resides inperiodically reversing the current fl'ow in any given kiln. The deliveryof air from one kiln to another, designedly and in such controllable wayas to insure the delivery of any definite proportion of air of anydefinite temperature or moisture content, is neither contemplated norpossible in the Duryea structure. The delivery'of air from one kiln toanother is possible but is not aisured in Duryea. Thereforeit is to beunderstood that the recitation in the appended elairns of the steps ofdelivering the air controllably at will from one kiln to another, meansa designed and predetermined control of the air in such way that theparticular kiln from which air is to be delivered and the particularkiln to-which air is to be delivered, will be under selection of theoperator,-and the duration of the delivery of air from one kiln to theother, independently of the duration of delivery to any other kiln, willbe at the will of the operator.

It is to be understood that the.invention is not limited to the preciseconstruction set forthbut that it includes within its purview whateverchanges fairly come within either the terms or the spirit of theappended claims.

Having described my invention what I claim is:

1. The combination with a battery of driers having their, usual maincirculatory systems, of connecting ducts between all of said drierswhich are in addition to and auxilia'ry to said main circulatory systemsand are arranged to controllably deliver at will .waste vapors from thedrying chambers of some of said driers to others of said driers.

. 2. The combination with a battery of driers having their usual maincirculatory systems, of asuction duct common to all of said driers,individual and independent controlling dampers for the several driersleading into said suction duct and means for deliveringvapors from saidsuction duct into another of the driers, said suction'ducts and vapordelivering means being in addition to and auxiliary to the said maincirculatory systems.- Y

3. The combination with a battery of driers and their usual maincirculatory; systems of 'a suction duct common to all ofsaid driers,individual and independentcontrolling dampers for each of said driersinto said suction duct, a pressure duct to which the suction duct isconnected, said pressure duct be ng common to all of said driers and1ndividual and independent controlling dampers in the pressure duct foreach of the driers.

4. A structure as recited in claim 3 incomtrolling dampers for and anautomatic relief element in said line adapted to discharge the vaporstherefrom when the pressure in said line reaches a predetermined degree.1

6. The combination with a battery of driers, each of said driers havingits longitudinally extending main pressure and suction ducts and mainheating means therein,-of an auxiliary suction duct common to all ofsaid driers, an auxiliary pressure duct common to all of said driers andhaving ports communicating withthe suction ducts of the respectivedriers, individual and independent consaid ports. individual andindependent controlling dampers between the several driers and theauxiliary suction ducts, connections between the auxiliary suction ductand the auxiliary pres sure duct to cause these ducts to constitute aclosed path, a fan disposed in said closed path, an automatic ventpermitting'the escapeof pressure from said path when the pressuretherein has reached a predetermined. degree.

7. A structure as recited in claim 6 in combination with a damperin saidpath for determining the degree of recirculation of the airtherethrough.

8. A structure as recited in claim 6 in combination with conditioningmeans disposed in said path.

, between each of nections between 9. The combination with a battery ofdriers, each of said driers comprising a drying chamber havinglongitudinally extending main pressure and suction ducts associatedtherewith and having main air circulating means and main heating meansassociated with said pressure and suction ducts, --the wholeconstituting a main circulatory system for each of the driers, of anauxiliary suction duct common to all of said driers and individualsuction laterals 7 extending along each of thedrying chambers andconnected to the last named suction duct, individual controlling damperssaid laterals and the'suction duct with which they are connected, anauxiliary pressure duct common to all of said driers and having port'scommunicating with the, circulatory systems of the.

respective driers, individual and independent controlling dampers forsaid ports, conthe auxiliary suction duct and the auxiliary pressure'duct to cause these ducts to constitute a closed path, and means forsetting up a circulation of air in said closed path.

10. A structure as recited in claim 9 in combination with an automaticvent permitting the escape of pressure from said path when the pressuretherein has reached a predetermined degree.

11. A structure as recited claim 9 in combination with a damper in saidpath for the air therein. I

12. A structure as recited in claim 9 in combinationwith airconditioning means disposed in said path.

13. The herein described method of controllingconditions in a battery ofdriers of a nature wherein the whole drying operation is effected by thecirculation of heated air and wherein the material being dried has adetermining the degree of recirculation of cpnsiderable moisture contentat the,beginning of the drying operation, which con- SlSl'S of settingup a main circulation of heated air through each of said driers andcontrollably withdrawing, at will, some of said heated air and thevapors of the moisture drivenoif'thereby, from any kiln and controllablydelivering the same at will to any other kiln.

14. The herein described method of controlling conditions in a batteryof driers of a nature wherein the whole drying operation is effected bythe circulation of heated air and wherein the material being dried has aconsiderable moisture content at the beginning of the drying operation,which consists of setting up a main circulation of heated air through.each of said driers and controllably WithdraWing at will, some of saidheated air and the vapors of the moisture driven ofl' thereby, from anykiln in an advanced stage of drying, delivering the same atwill to anyother kiln in a less advanced stage of drying.

15. In combination, a battery of kilns, a main circulating system foreach of said kilns, each main circulating system comprising pressureanchsuction air ducts, means for heating the air therein and means forsetting up a circulation of air therein and an auxiliary circulatingsystem having individually. controllable connections with the dryingchambers of each of said kilns and individually controllable connectionwith the main suction ducts of the several main circulating systems ofthe various kilns.

In testimony whereof I atfix my signature.

MORITZ L. MUELLER.

and controllably

